Dec. 7, 2010 -- Extremely high levels of a fire retardant found in a sample of butter show the need for better monitoring of the nation's food supply, researchers say.

Levels of the chemical retardant polybrominated diphenyl ether (PBDE) in the sample were 135 times higher than the average for nine other tested samples.

Researchers say the contamination appears to have come from the butter's paper wrapper, which had PBDE levels that were more than 16 times greater than levels in the butter.

The contamination was discovered during a routine sampling of various foods in an effort to better understand the prevalence of PBDE and other chemical contaminants in the foods we eat.

PBDE Levels in Foods Not Known

Investigators say the incident represents the worst documented case of PBDE contamination in food ever reported in the U.S.

But lead researcher Arnold Schecter, MD, says this may be because no one is really looking for the flame retardant or related chemicals in the nation's food supply.

Schecter is a professor of environmental sciences at the University of Texas School of Public Health in Dallas.

“We hope that investigations like ours will inspire the U.S. government to follow this more closely,” he tells WebMD. “Government inspectors may be out there occasionally looking for E. coli in hamburger, but there seems to be no system for monitoring level of chemicals in foods.”

A spokeswoman for the chemical industry was highly critical of the study, which was published in the journal Environmental Health Perspectives, published by the National Institutes of Health.

“This is an invalid, unscientific study of 10 sticks of butter from one city; it is inappropriate for a federal agency publication, under the cloak of science, to use citizens' tax dollars to legitimize it,” American Chemistry Council Director of Product/Panel Communications Kathryn St. John says in a written statement to WebMD.

Flame Retardant Is Everywhere

PBDEs have been used since the 1970s in the manufacture of plastics, electronics, fabrics, and foam used in the cushions of couches and upholstered chairs.

PBDEs are stored in the body, and monitoring programs in Europe, Asia, North America and even the Arctic have found traces of PBDEs in human breast milk, fish, and birds.

Although the health effects of this exposure are not well understood, studies in animals have linked PBDEs to liver toxicity, thyroid toxicity, developmental delays, and infertility.

Safety concerns led the Environmental Protection Agency (EPA) to phase out the manufacture of the widely used PBDE compounds penta-BDE and octa-BDE several years ago, and manufacturers have agreed to stop making and using the compound deca-BDE within the next few years.

The newly published investigation was part of a three-year study of chemical contamination in U.S. foods, funded by the nonprofit public health research group Pfeiffer Research Foundation.

The analysis included several hundred foods purchased at five Dallas-area supermarkets on two occasions in 2009, including different brands of butter.

Schecter and colleagues report that in the highly contaminated sample, levels of the deca-BDE component BDE-209 were 900 times higher than the average of the other nine butters tested.

Is Food Packaging Adding to Exposure?

Schecter says it is not clear if the contamination was an anomaly or represents a much bigger problem than has been realized.

“It is clear that some of the foods we buy are contaminated with these flame retardants, and that in some, hopefully rare, cases levels are strikingly high.”

University of California, Berkeley assistant professor Kim Harley, PhD, says the study raises concerns that food packaging may be a previously unrecognized source of chemical contamination, especially in high-fat foods like butter.

Harley is the associate director of the UC-Berkeley School of Public Health's Center for Children's Environmental Health Research. Her own PBDE study, published in January, suggested a link between high levels of BPDE and decreased fertility in women.

Research suggests that as many as 97% of Americans have some PBDEs in their blood, but Harley says how the chemicals got there is still something of a mystery.

“We think the major culprits are house dust and foods, but there is a lot we are still learning about where our exposure comes from,” she says.

Since PBDEs are fat soluble, Schecter says people who eat fewer animal products probably have less exposure.

“We know that these chemicals accumulate in animal fat, so cutting the fat of meat and salmon and drinking skimmed milk instead of whole may help reduce exposure,” he says.